PromiseCoerce should ignore primitive values.
PromiseCoerce should ignore primitive values.

PromiseCource(x) should return "not a thenable" if Type(x) is not Object
even if x.then exists.

BUG=347095
LOG=Y
R=rossberg@chromium.org

Review URL: https://codereview.chromium.org/194403002

Patch from Yutaka Hirano <yhirano@chromium.org>.

git-svn-id: b158db1e4b4ab85d4c9e510fdef4b1e8c614b15b@19788 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh